Poly Painting UVs

From ZBrush Info

Remapping UV Coordinates

Polypainting allows you to easily remap UV coordinates. This can be a major advantage if you find that, for some reason, the original UV mapping for your base mesh must be changed. Here's how:

1. A base mesh is imported. For simplicity, we'll assume this mesh has UV coordinates applied already.
2. The mesh is sculpted and painted, and a texture map is generated and exported.
3. At some point, it becomes obvious that the original UV mapping is not satisfactory (perhaps it doesn't give enough detail in some areas, or creases are visible). In your external application, a new UV mapping is generated and applied to the base mesh.
4. The model is selected in ZBrush at the base mesh subdivision level, and the newly mapped external base mesh is imported over that base mesh. The imported base mesh, along with its new UV coordinates, replaces ZBrush's base mesh for the model, but does not affect the polypainting of the model.
5. You can now generate a texture map from the polypainted ZBrush model, exactly as before.

Some points to note:

• Importing the new base mesh may change the geometry of the base mesh in ZBrush. If you use Tool:Morph Target:StoreMT before importing, you can then use Tool:Morph Target:Switch to switch back to the original geometry.

Also, if you have an existing texture you need to remap, you can:

1. Use Tool:Texture:TxrCol to polypaint the selected texture onto the model in ZBrush. Of course, the UV mapping of the model at this point must match the texture that was generated using that UV mapping.
2. If you wish, use polypainting to sharpen areas, add details, etc.
3. Remap the polypainting to a new texture map as described above.